Add some wtperf workloads that turn logging on.
Push the checkpoint program a little harder, it's failing in some
more complex cases in the new insert-split branch.
Don't drop core on LSM-only runs, we can't open a cursor to verify with.
Merge pull request #1415 from wiredtiger/wtperf-log-workloads

Add some wtperf workloads that turn logging on.